The present invention relates to transmission gears, particularly for ship drive and propulsion systems.
Transmission gears are, for example, constructed in that the drive shaft or input axle is drivingly coupled to a spur gear on an intermediate shaft which drives two pinions which are aligned with the intermediate shafts and are arranged to both sides of the spur gear. The pinions in turn mesh with two large gears on the output drive shaft.
The manufacture of spur gear drives is difficult for high power transmission gears such as in ship drive systems. It may well occur that the dimensions of the gears exceed the power capabilities of tooth making machines. In order to solve the problem inherent in the situation one uses frequently the principle of power branching. Specifically, the power for a ship's drive is divided into two branches by means of separate spur gears meshing the pinions which are coupled to the input shaft. Each spur gear sits on an intermediate shaft to divide further the power in the two branches in that each intermediate shaft drives two pinions. This way one obtains four branches, which, of course, have to be combined on the single output shaft. One has used here large gears on that shaft, each meshing with two of the four pinions. Such a transmission gear, operating with two cascaded power branchings and using just two large gears for driving the output shaft is quite satisfactory, but the load distribution as between the four pinions and the two large gears requires improvement. For example, in the case of a ship drive system contour changes and resilient yielding of the ship's hull is inevitable, depending on the sea, temperature, etc. so that parts of the drive system being supported at different locations are inevitably displaced in relation to each other. Also, some tolerances and initial alignment errors interfere with the power branching and the desired uniform local distribution.